Retorting total raw shale



United States Patent Ofifice 3,489,672 RETORTING TOTAL RAW SHALE Bernard L. Schuman, Livington, and Herbert P. Dengler, Fairhaven, N.J., assignors to Esso Research and Engineering Company Filed Dec. 7, 1966, Ser. No. 599,940 Int. Cl. Cg 1/02; C10b 57/04, 53/06 US. Cl. 208-11 10 Claims ABSTRACT OF THE DISCLOSURE Oil shale fines are retorted in admixture with larger fines by slurrying the fines in a liquid vehicle, such as oil or water, and introducing the slurry into the retort at a selected point where the temperature is sufiicient to decompose the kerogen in the fines to shale oil but insufficient to crack the shale oil.

The present invention is directed to the mining and retorting of oil shale. More particularly, the invention is concerned with the mining and retorting of oil shale where particles of raw oil shale having larger and smaller particle diameters are mined and retorted. In its more specific aspects, it is involved with the retorting of smaller diameter particles of oil shale which heretofore have not been retorted and which heretofore have been discarded.

The present invention may be briefly described as a method of retorting small particles of oil shale to recover shale oil therefrom. Ordinarily, in the mining and retorting of oil shale, particles of raw oil shale having diameters both larger and smaller than from about 0.2 to about 0.3 inch are obtained. The particles larger than about 0.2 to about 0.3 inch are treated in a combustion retorting operation involving passage of the larger particles through preheating, retorting, combustion, and cooling zones..The smaller particles (hereinafter sometimes called fines) having diameters smaller than about 0.2 to about 0.3 inch heretofore were not retorted and normally were discarded. In the practice of the present invention the smaller particles are admixed with a liquid vehicle to form a slurry of the smaller particles in the vehicle. The resultant slurry is then introduced into the combustion retorting operation wherein the larger particles are being treated. The slurry is introduced into the retorting operation preferably at a point where the temperature is sufficiently low to avoid cracking of the shale oil recovered from the smaller particles, but at a point where the temperature is sufficiently high to decompose kerogen in the smaller particles to shale oil. Thereafter, shale oil from both the larger and smaller particles is recovered.

The point where the slurry is introduced may be a point just above the retorting zone. Preferably, the slurry is introduced into the gas combustion retorting operation, particularly when the liquid vehicle is oil, at a point in the gas combustion retorting operation where the temperature is within the range from about 500 to about 700 F. This point may be just above, or at least adjacent to, the retorting zone which allows the evaporation of the oil in the slurry and allows the fine shale particles to be quickly heated to a kerogen-decomposition temperature of about 750 F.

The liquid vehicle, which is used to form a slurry of the raw shale fines having particle diameters smaller than about 0.2 to about 0.3 inch, may suitably be water, oil, or other liquid organic materials. When the liquid vehicle is water, it may be water produced in the gas combustion retorting operation, or it may be water added from an extraneous source. When the liquid vehicle is oil, it may be a portion of the shale oil products produced in the gas combustion operations or a fraction thereof. However, it

3,489,672 Patented Jan. 13, 1970 is to be understood that the oil may be any normally liquid hydrocarbon or oil obtained from any source extraneous to the operation.

The amount of liquid vehicle used in the operation is not particularly critical, but should be an amount sufiicient to provide a pumpable slurry. As an example only, the slurry may be made up of about equal parts of liquids and solids, but may be made up from 1:1 to about 2:1 parts per weight of liquid vehicle and raw shale having particle diameters less than about /1. inch.

It is within the contemplation of the present invention that the slurry of raw shale fines in oil or water may be introduced into the gas retorting operation at a single or at a plurality of points. Thus, when the liquid vehicle is oil, it would be desirable to introduce the slurry into the retorting operation immediately above the retorting zone where the temperature is suitably within the range from about 500 to 700 F. When the liquid vehicle is water, the slurry may be introduced at a point closer, or at least adjacent to, the retorting zone since there is no danger of cracking the slurrying vehicle, and the presence .of water tends to minimize excessive temperatures, such as temperature peaking. It is, also, within the purview of the present invention that when the liquid vehicle is water, the slurry may be introduced into the retorting zone or into a plurality of zones along with a suitable gas which may be the recycle gas, or an extraneously provided gas, such as, but not limited to, steam, hot combustion products of recycle gas and air, natural gas, and the like.

The present invention will be further illustrated by reference to the drawing in which the sole figure is a flow diagram of a preferred mode and embodiment. Referring now to the drawing, numeral 11 designates a feed line in which raw oil shale, having particle diameters larger than about A inch and usually within the range from about /8 to about 3 inches in diameter, depending on the crushing procedures used, is introduced into a gas combustion retorting vessel 12. Gas combustion retorting vessel 12 comprises a preheating zone 13, a retorting zone 14, a combustion zone 15, and a cooling zone 16. The raw oil shale flows serially downwardly through the several zones and the spent shale, which comprises about to about of the raw oil shale, is discharged by way .of line 17 to a waste pile which may be located some distance from the gas retorting vessel 12.

Heat and gases for retorting and preheating the oil shale are provided by introducing into the combustion zone 15 by way of line 18, controlled by valve 19, a sufficient amount of air to cause combustion of carbonaceous material on the descending shale. The amount of air employed may range from about 4,000 to about 6,000 standard cubic feet per ton of raw oil shale introduced into the operation, including fines. This combustion operation provides a temperature in the combustion zone which may suitably range from about 1,000 to about 1,400 F., but usually Within the range of about 1,200" to about 1,400 F. The resultant heat and the ascendant flue gases cause retorting and decomposition of the kerogen in the oil shale to shale oil in retorting zone 14. The released shale oil flows upwardly into preheating zone 13 and the heat contained therein preheats the raw oil shale introduced by line 11. Thus, the temperature in the preheating zone may be within the range from about 400 to about 800 F., usually about 600 F. The temperatures in the retorting zone 14 may be within about the range of 600 to 1,000 F.; usually from-about 700 to 950 F.

The temperatures in the cooling zone 16 will usually range from about 1400 to 200 F., usually about 400 F.

As stated, the temperature where the slurry is introduced may be within the range of about 500 to 700 F.

Pressures in the several zones may range from 0 to about 100 p.s.i.g. Preferably a pressure within the range from about to about 60 p.s.i.g. may be used.

As a result of the gas combustion retorting operation in vessel 12, a vaporous product is Withdrawn by way of line 20 and passed through a condenser-cooler 211, and thence into an oil mist recovery drum 22, provided with a Water leg 23, wherein a separation is made among non-com densable gas, shale oil, and water produced in the operation. The non-condensable gases may be discharged by line 23A from the system by opening valve 24A, but preferably a major part of this gas is recycled by line 25A controlled by valve 26A to the gas combustion retorting vessel 12 where the recycle gas serves to cool the spent shale in cooling zone 16. The amount of recycle gas may be within the range from about 12,000 to about 20,000 standard cubic feet per ton of raw oil shale introduced into the operation, including fines.

If desirable, the recycle gas may be augmented by an extraneously supplied gas through line 27A which connects to line 25A controlled by valve 28A.

The water accumulating in water leg 23 may be discharged therefrom by line 24, and thence from the system by branch line 25, and line 26 controlled by valve 27. Preferably, however, the water in Water leg 23 is intro duced by opening valve 28 in line 25 into line 29 and, thence, into a slurry drum 30 into which raw shale fines, having particle diameters less than about A in-ch, are introduced by line 31A from the oil shale mining and crushing operation. The slurry is formed in slurry drum 30 by means of a mixing device 31, which may be powered with a suitable power means.

The slurry in slurry drum 30 may then be introduced into the gas combustion retorting vessel 12 as will be described further.

It may be desirable to use an extraneous source of water as the liquid vehicle in making up the slurry, and under these instances the water from an extraneous source, which may be fresh Water or brine, may be connected to line 26B and introduced by opening valve 32.

The slurry may also be made up using a portion of the shale oil. In this instance, shale oil is discharged from oil mist recovery drum 22 by line 33, and a portion thereof withdrawn as product by line 34. A smaller portion is discharged by line 33 controlled by valve 35 into slurry drum 30. Of course, the oil may be from an extraneous source, and when it is desired to use oil produced outside the operation, or from any source, valve 36 in line 37 connecting to the outside source of oil may be opened.

As mentioned, when the liquid vehicle is oil, the slurry will preferably be introduced above the retorting zone 14 into a zone 13A, which may be at a temperature Within the range of about 500 to about 700 F. To this end, the slurry is withdrawn from slurry drum 30 by line 38 and introduced into zone 13A by charge line 39 controlled by valve 40. When the liquid vehicle is water, however, the slurry may be introduced at a point nearer to, or just adjacent to, the retorting zone 13 and to this end, line 41 controlled by valve 42 is provided to allow the slurry comprising water and fine shale particles, to be introduced at least adjacent to the retorting zone 14 and sometimes in the retorting zone 14.

Also, when the liquid vehicle is water, the slurry may be introduced into the retorting zone 14, particularly when a gas is also introduced with the slurry. To this end, line 43, controlled by valve 44, is provided for introduction of the water-raw shale fines slurry directly into the retorting zone 14 with gas which may be recycle gas obtained from line 25A, to which line 43 connects, by opening valve 45. The gas, however, may be other gases, such as air, steam, natural gas or the hot combustion products of recycle gas and air, and the like, but not limited thereto, obtained from a source extraneous to the operation. This may be done by opening valve 46 in branch line 47 which connects to such a source of gas.

The present invention is quite important and useful in that numerous advantages inure to introduction of raw shale fines into the gas combustion retorting operation as a slurry in a liquid vehicle. Thus, when oil is employed, it has been found that if such oil is introduced above the retorting zone, the oil would not be cracked since the oil is evaporated and recovered without loss, thus providing for introduction of fines from which shale oil is recovered. The fines may usually comprise from about 10% to 20% by weight of the oil shale which is mined and crushed, which ordinarily would have to be discarded. It is to be understood, however, that the fines may comprise a lesser amount of the oil shale and may be Within the range of about 1% to about 20% by weight and may be from about 5% to about 10% of the raw oil shale. Thus, the fines provide an additional source of oil shale in a very economical fashion, thus providing for recovery of a greater amount of shale oil than heretofore possible. The invention is not to be restricted to any particular amount of fines.

The advantages are also marked where water is the liquid vehicle since a greater amount of shale oil may be stripped from the oil shale rock without danger of cracking the oil, if it were used as the liquid vehicle. Vaporization of water used as the liquid vehicle is advantageous since temperature peaking may be minimized. Furthermore, the steam generated by evaporation allows reaction with the spent shale of the off-gas as well as improving liquid yields of shale oil. Another advantage of using Water produced from the process, or other aqueous streams, is that ordinarily pollutant water streams may be disposed of by using them as a slurrying agent. Thus, in accordance with the present invention, excessive temperatures may be avoided, greater recovery of shale oil is obtained, and streams, which would normally be pollutants if disposed of in rivers, and otehr surface sources, and the like are disposed of without causing pollution.

The mining and crushing of oil shale has not been described in that these operations are conventional. The oil shale may be obtained by room and pillar mining of oil shale obtained anywhere in the world, but particularly from the western states of the United States, and specifically from Colorado. The usual crushing of the mine oil shale produces particles ranging from dust up to particles having the diameters which have been given heretofore. The present invention allows the recovery of shale oil from the particles having the small diameters which heretofore have not been handled economically.

The nature and objects of the present invention, having been completely described and illustrated, and the best mode and embodiment contemplated set forth, what we Wish to claim as new and useful and secure by Letters Patent is:

1. In the mining and retorting of oil shale wherein particles of raw oil shale having diameters both larger and smaller than about 0.2 to about 0.3 inch are obtained and wherein said particles larger than about 0.2 to about 0.3 inch are treated in a combustion retorting operation in which heat is provided by burning carbonaceous material on the shale involving passage of said larger particles downwardly through preheating, retorting, combustion, and cooling zones and wherein said particles smaller than about 0.2 to about 0.3 inch are normally discarded without retorting, the method of retorting said smaller particles of raw oil shale in said combustion retorting operation with said larger particles to recover shale oil therefrom comprising:

admixing said smaller particles with a liquid vehicle to form a slurry of said smaller particles in said vehicle;

introducing said slurry into said combustion retorting operation and admixing same with said larger particles at a point where the temperature is sufficiently low to avoid cracking of the shale oil recovered from said smaller particles but Where the temperature is sufficiently high to decompose the kerogen in said smaller particles to shale oil; and

recovering shale oil from the kerogen in both said larger and smaller particles.

2. A method in accordance with claim 1 in which the smaller particles are introduced into said gas combustion retorting operation at a point above the retorting zone.

3. A method in accordance with claim 1 in which the smaller particles are introduced into said gas combustion retorting operation where the temperature is within the range from about 500 to about 700 F.

4. A method in accordance with claim 1 in which the liquid vehicle is water.

5. A method in accordance with claim 4 in which the water is water obtained in said combustion retorting operation.

6. A method in accordance with claim 1 in which the liquid vehicle is oil.

7. A method in accordance with claim 6 in which the oil is shale oil.

8. A method in accordance with claim 1 in which the smaller particles comprise about 1% to about 20% of the mined oil shale.

References Cited UNITED STATES PATENTS 3,004,898 10/1961 Deering 202-16 3,074,877 1/ 1963 Friedman 20811 3,349,022 10/ 1967 Mitchell et al 20811 3,384,569 5/1968 Peet 20811 DELBERT E. GANTZ, Primary Examiner T. H. YOUNG, Assistant Examiner US. Cl. X.R. 201-15, 23 

